When you've got through the long years of university training and you've got your PhD and you're a real scientist, how should you start to tackle your first problem? Well, I think a very useful thing to do is to challenge the dogma, the conventional wisdom that your colleagues around you tell you is the basis of the science of the problem you're working on. Challenging conventional wisdom is the way to make waves in science. And let me give you a very simple example. When I first went to work for the Medical Research Council in 1941, one of the problems we had was how do aerial disinfectants works? The reason we were interested, there was great fear there would be influenza epidemics under the packed conditions of tube shelters in London during wartime. And they used to go around spraying the air with aerial disinfectants to kill any airborne organisms that were present. And one of the problems was how do they work and can we make better ones? And the conventional wisdom was that the organisms were killed by droplets of the disinfectant floating in the air colliding with them. Well, for some reason this seemed to me very dubious. I thought, I don't believe it, it doesn't make sense. And I did the sums and it soon came out that, knowing how many disinfectant particles and how many bacteria were floating in the air, that it would days if not weeks for collisions to occur. And yet we knew from experiments that the organisms were killed in seconds or at the most minutes. So something different was happening - what? And it was some… a few fairly simple experiments, I was able to show that the organisms were killed by the vapor of the disinfectant distilling over from the disinfectant droplets onto the bacteria and thereby killing them. And with that knowledge I was able to invent very much more effective aerial disinfectants that were very much more toxic to organisms and less toxic to people. In fact, the best one turned out to be simply lactic acid, which is a natural component in your body, but if you vaporise it in the air it kills an organism faster than anything.

And so, that's challenging the conventional wisdom and of course that has been my pitch throughout most of my lifetime. When I was working on freezing, the nature of freezing damage, the conventional wisdom was that cells or tissues or whole animals are damaged when they are frozen by the ice crystals penetrating the cells and sort of mechanically breaking them up. Indeed, they had film showing this happening on a microscope, freezing microscope, freezing microscope slide of the ice crystals penetrating this way. It all seemed very real. Being my usual sceptical self I thought I wonder if this true? And I imagine myself a cell being frozen. I thought, what happens? Well water is going to, when it starts forming ice crystals it'll form small ones at first which shouldn't be too intrusive, but it's going to separate as a pure substance, it always does; ice is pure water. So what happens to the things that are left behind? Cells float in a slightly salt solution, the salt would become concentrated and quite rapidly it became clear to me that in no time in freezing, the salt concentration would rise to the level of pure brine. At minus 20 it's five molar. Five is the, you know, saturated salt. And this is what kills all cells very rapidly. And a few experiments demonstrated that you can account for virtually all of the damage that occurred to living cells when they were frozen under the conditions that my colleagues were freezing, which is slow freezing by the concentrating of the salts in the solution. The ice crystals had nothing whatever to do with it.

And this led in practice to the invention of better antifreeze agents to prevent it. And one of them was dimethyl sulfoxide which has been used in freezing eggs and things, for keeping - human eggs - for keeping them for long-term for fertilisation procedures. And so on. And of course, in the work I did on the self-regulating Earth, the Gaia Theory, the great conventional wisdom of biology and of geology, come to that, is that organisms adapt to their environment. That is the great dogma of the subject. Well, it's something to think about. It assumes that the environment is a given, determined by the chaps who work in the other building of the university, the geologists, not by the biologists. The geologists, of course, assume that the biology does nothing to their evolution of the rocks, that the two processes are quite separate.

And the way to look on Gaia Theory is that it's a new theory of evolution, which sees the evolution of the organisms and the evolution of the Earth, the rocks, the air and the ocean, not as separate processes, but as two tightly coupled processes, evolving together. You see, everything alive changes the environment. You can't help it. You breathe out carbon dioxide you're changing the atmosphere. When you breathe in oxygen you're taking the oxygen away. Just with two examples everything alive is influencing its environment. So, we are not evolving in a geological given, we're evolving in a world that our ancestors have made. You could say we're evolving in a world which is made of the breath, the bones and the blood of those that went before us. And this comes from challenging the dogma that things just adapt to that Earth that's there, a given.

Born in Britain in 1919, independent scientist and environmentalist James Lovelock has worked for NASA and MI5. Before taking up a Medical Research Council post at the Institute for Medical Research in London, Lovelock studied chemistry at the University of Manchester. In 1948, he obtained a PhD in medicine at the London School of Hygiene and Tropical Medicine, and also conducted research at Yale and Harvard University in the USA. Lovelock invented the electron capture detector, but is perhaps most widely known for proposing the Gaia hypothesis. This ecological theory postulates that the biosphere and the physical components of the Earth form a complex, self-regulating entity that maintains the climatic and biogeochemical conditions on Earth and keep it healthy.